In the magnetic media industry, high-performance, thin-film media are produced by depositing successive layers on a substrate. Apparatus for preparation of such media are well known in the art, and for media of the type formed on a rigid disc substrate, typically in such an apparatus each layer in the medium is deposited in a separate processing chamber. For example, the underlayer, the magnetic layer and the overcoat layer are generally deposited in separate processing chambers.
The main or common transport chamber in the apparatus during preparation of the medium is maintained at a low working pressure, e.g. typically less than about 5.times.10.sup.-7 Torr, by means of a high performance vacuum pump. The processing chambers in the apparatus are positioned along the main chamber and receive substrates for sequential processing.
One problem with the conventional deposition apparatus is cross-contamination of deposition materials between the processing chambers. For example, after deposition of a carbon overcoat onto a magnetic medium and removal of the substrate from the carbon-overcoat processing chamber for transfer to a processing chamber downstream, carbon and/or other materials in the carbon-overcoat processing chamber can migrate to any of the other chambers in the apparatus, including those chambers for deposition of the magnetic recording layer and the underlayer. This is particularly a problem when a carbon overcoat is deposited by ion beam deposition, since any remaining gas, e.g., ethylene, in the chamber can readily migrate to other chambers. Naturally, is such cross-contamination is undesirable, since it can effect the properties of the medium.
Another problem encountered with preparation of carbon overcoats in conventional deposition apparatus is buildup of particulate contaminants within the processing chamber. This problem is encountered when carbon overcoats are deposited from a graphite sputtering target and by ion beam deposition. The particulate matter must be removed from the apparatus before it begins to flake and peel causing defects in the medium. Removal of the particulate contamination typically necessitates a shut-down of the apparatus, reducing productivity.